Behavior is:› What animals do › how they do it› Why they do it

Includes learning

the scientific study of animal behavior, particularly in natural environments

a sequence of unlearned, innate behaviors that is unchangeable› usually carried to completion

triggered by an external sensory stimulus › sign stimulus

Ex. male stickleback fish attack behavior › the stimulus is the red underside of an

intruder

BEHAVIOR: A male stickleback fish attacks other male sticklebacks that invade its nesting territory.

PROXIMATE CAUSE: The red belly of the intruding male acts as a sign stimulus that releases aggression in a male stickleback.

ULTIMATE CAUSE: By chasing away other male sticklebacks, a male decreases the chance that eggs laid in his nesting territory will be fertilized by another male.

includes learning and innate components › generally irreversible

sensitive period› limited developmental phase that is the only

time when certain behaviors can be learned

Ex. young geese following their mother

BEHAVIOR: Young geese follow and imprint on their mother.

PROXIMATE CAUSE: During an early, critical developmental stage, the young geese observe their mother moving away from them and calling.

ULTIMATE CAUSE: On average, geese that follow and imprint on their mother receive more care and learn necessary skills, and thus have a greater chance of surviving than those that do not follow their mother.

Conservation biologists saving whooping cranes from extinction

simple change in activity or turning rate in response to a stimulus

Ex. sow bugs become more active in dry areas and less active in humid areas

Kinesis increases the chance that a sow bug will encounter and stayin a moist environment.

Dry openarea

Moist siteunder leaf

automatic, oriented movement toward or away from a stimulus

stream fish exhibit positive rheotaxis; they automatically swim in an upstream direction› prevents them from being swept away › keeps them facing the direction from which

food will come

Positive rheotaxis keeps trout facing into the current, the directionfrom which most food comes.

Directionof rivercurrent

Migration

pheromones

Minnows are widely dispersed in an aquarium before an alarm substance is introduced.

Within seconds of the alarm substance being introduced, minnows aggregate near the bottom of the aquarium and reduce their movement.

modification of behavior based on specific experiences

form of learning that involves loss of responsiveness to stimuli that convey little or no information

Operant conditioning › type of associative learning in which an

animal learns to associate one of its behaviors with a reward or punishment

also called trial-and-error learning

Cognition

Product of sexual selection

Promiscuous› no strong pair-bonds or lasting relationships

monogamous › one male mates with one female

Since monogamous species, such as these trumpeter swans, are often monomorphic, males and females are difficult to distinguish using external characteristics only.

Polygyny› one male mates with many females› males are often more showy and larger than

the females

Among polygynous species, such as elk, the male (left) is often highly ornamented.

polyandrous systems› one female mates with many males› females are often more showy than the

males

In polyandrous species, such as these Wilson’s phalaropes, females (top) are generally more ornamented than males.

intersexual selection› members of one sex choose mates on the

basis of certain traits Intrasexual selection

› competition between members of one sex for mates

can reduce variation among males agonistic behavior

› ritualized contest that determines which competitor gains access to a resource

reduce their individual fitness but increase the fitness of others

Ex. Naked mole rat populations › nonreproductive individuals may sacrifice

their lives protecting the reproductive individuals from predators

the total effect an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring

Three key variables in an altruistic act:› Benefit to the recipient› Cost to the altruist› Coefficient of relatedness (the probability

that if two individuals share a parent or ancestor, a gene in one individual will also be present in the second individual)

Altruistic behavior toward unrelated individuals

can be adaptive if the aided individual returns the favor in the future